The relationships between food and energy intakes, salt content and sugar types in Egyptian fruit bats

Abstract

Frugivorous animals may face an osmoregulatory challenge due to the watery nature of their food and low concentration of electrolytes therein. We examined the effects of salt content (NaCl) and sugar type (sucrose vs. glucose) on the intake rate of dilute sugar solutions by the Egyptian fruit bat (Rousettus aegyptiacus). Increased salt content did not bring about an increase in energy intake by bats fed dilute sucrose diets and the bats did not compensate by hyperphagia to achieve the energy intake of bats fed concentrated sucrose solution without salt. Moreover, increasing salt content had a negative effect on the total energy intake of Egyptian fruit bats fed equicaloric sucrose solutions. There were no differences in hematocrit in bats fed the diets of different sucrose concentration, but plasma osmolality was higher in those bats fed more concentrated sugar solutions, and urine osmolality was higher in those fed on highsalt diets. Food and energy intake did not differ between bats that were fed dilute glucose and sucrose solutions. Our findings indicate that Egyptian fruit bats do not modulate food intake when salt content of dilute sugar solutions is increased, and that increasing salt content might constrain their food intake rate. Sugar type did not affect food intake by Egyptian fruit bats, indicating that sucrose hydrolysis alone does not limit the intake of dilute sugar nectar.

Sugar and nitrogen digestive processing does not explain the specialized relationship between euphonias and low‐quality fruits

“…The same procedure outlined above was used to test for within‐ and between‐species differences in fractional changes in m b (Δm b , calculated as in Herrera et al 2015) as a function of sugar concentration. In this case, however, we did not use m b as a covariate in the GLM model to avoid collinearity.…”